Which waveform is used to generate a motor response?

• A. Exponential
• B. Rectangular
• C. Balanced
• D. Sine

Answer: (C)

To generate a motor response, you need a brief, sharp depolarization of the nerve with a waveform that is safe for repeated use. A balanced biphasic pulse provides equal positive and negative charge in each cycle, so there is no net DC accumulating in the tissue or at the electrodes. This charge balance protects tissues and electrodes while still reliably triggering muscle contraction. The rectangular shape helps achieve a quick rise to threshold, but the key aspect is balancing the charge—without it, safety and consistency over multiple pulses are compromised. Other waveforms may be less efficient or riskier for motor stimulation, making the balanced waveform the best choice.